Beard, R. M. (1969). An outline of Piaget's developmental psychology for students and teachers. Routledge & Kegan Paul.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रBeard, Ruth M. An Outline of Piaget's Developmental Psychology for Students and Teachers. Londres: Routledge & Kegan Paul, 1969.
एमएलए (9वां संस्करण) प्रशस्ति पत्रBeard, Ruth M. An Outline of Piaget's Developmental Psychology for Students and Teachers. Routledge & Kegan Paul, 1969.
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